This invention relates to improvements in disc mills or refiners and, more particularly, to the refiner plates which determine their useful function. It will be described, by way of illustration, and not by way of limitation, with reference to certain preferred embodiments which have, in test, proven to have special advantage and to lend a significant advance in the art of milling corn starch.
In milling corn starch the corn kernels from which the starch is extracted are passed through several separating stages, first to remove the germ and then the starch. The removal of the starch is particularly difficult since it adheres very tightly to the fibrous structure of the corn hull which forms its natural casing. Disc refiners are presently applied to this task. While it appears to be the best apparatus available for this purpose, experience indicates that such apparatus has had a limited ability to break an appreciable amount of starch loose from the hulls of corn kernels during a single pass of the de-germed kernels between its refiner plates. Contributing to the difficulties of overcoming this problem is the fact that if the refiner plates are set too closely together when applied to the separation of the corn starch, the teeth of the plates will cut and grind the fibrous corn hull. The result of this is to create fiber particles which in the process of extraction of the starch will clog the starch recovery system. This necessitates costly maintenance procedures, and shut down of the recovery operation while such procedures must be carried out. On the other hand, it has been found that due to the required spacing of the refiner plates to avoid this problem often times corn kernels will move from the inner to the outer radial limits of the plates between which they must pass through paths which circumvent the interdigited refiner teeth. Such problems as this contribute to the limited percentage of starch extraction that has been experienced in the use of a disc refiner as heretofore constructed and comprised.